Bicyclic ester-lactones



United States Patent 3,193,81t3 BICYCLIC ESTER-LACTGNES James C. Wygant,Creve Coenr, and Erhard .l. Frill, Des

Peres, Mo., assignors to Monsanto Qompany, St. Louis, Mo., a corporationof Delaware No Drawing. Continuation of application Ser. No.

144,539, Oct. 12, 1961, This appiication Aug. 3,

1964, Ser. No. 387,204

3 t'llairns. (6i. 2 50-3433) This application is a continuation of ourprior copending application Serial No. 144,589, filed October 12, 1961,now abandoned in favor of this application.

This invention relates to ester-lactones. In one aspect, this inventionrelates to bicyclic ester-lactones of the alkyl- M-tetrahydrophthalicanhydrides. in another aspect, this invention relates to methods forproducing bicyclic esterlactones of alkyl-A -tetrahydrophthalicanhydrides. In another aspect, this invention relates to methods for thealcoholysis/lactonization of alkyl-A -tetrahydrophthalic anhydrides.

In our copending application Serial No. 34, filed January 4, 1960, wedisclosed and claimed a process for the preparation of ester-lactones ofalkenylsuccinicanhydrides lby alcoholysis of the alkenylsuccinicanhydride to form an acid-ester and then acid-catalyzed lactonization ofthe acid-ester to form an ester-lactone of the alkenylsuccinicanhydride. Attempts to form the ester-lactones of theM-tetrahydrophthalic anhydrides by a similar process have resulted infailure with only the formation of diesters, not ester-lactones. t

We havenow discovered, much to our surprise, that the ester-lact-ones ofthe h -tetrahydrophthalic anhydrides can be formed by analcoholysis/lactonization process by substituting an alkyl substituenton the ethylenic linkage of the A -tetrahydrophthalic anhydride.

An object of this invention is to provide a process for producing abicyclic ester-lactone from an alkyl-A -tetrahydrophthalic anhydride.

Another object of this invention is to provide a process for reacting analkyl-A -tetrahydrophthalic anhydride with a monohydric alcohol to forma bicyclic ester-lactone.

Another object of this invention is to provide a process for esterifyingan alkyl-AF-tetrahydrophthalic anhydride to form an acid-ester of saidalkyl-A -tetrahydrophthalic anhydride.

Another object of this invention isto provide a process forlactonization of an acid-ester of an alkyl-A -tetrahydrophthalicanhydride to form a bicyclic ester-lactone.

Another object of this invention is to provide bicyclic ester-lactonesof an alkyl-h -tetrahydrophthalic anhydrides as new compounds.

; Other objects and advantages of this invention will be apparent to oneskilled in the art upon studying this disclosure. a

In accordance with this invent-ion, an alkyl-A tet-rahydrophthalicanhydride is reacted with a monohydric alco: hol to form a bicyclicester-lac-tone. The reactants are initially reacted preferably in theabsence of a catalyst and then an acid-type catalyst is employed tocomplete the reaction. The initial phase of the reaction involvesopening of the heterocyclic ring of the alkyl-Ai-tetrahydropht-halicanhydride and partial esterification thereof as illustrated by Equation.1:

"ice

wherein R is selected from the group consisting of hydrogen and alkyl, Ris alkyl, and R is hydrocarbyl. The final phase of the reaction requiresthe use of a catalyst and involves intramolecular 'cyclization of theacidester to form a bicyclic lactone substituted with an ester group, asillustrated by Equation 2:

wherein R R and R are as above defined. The use of catalyst in theinitial phase of the reaction tends to result in the formation ofdiesters instead of acid-esters or partial esters, and the formation ofthe diester prevents the intramolecular cyclization in the final phaseto form the bicyclic ester-lactone.

Further, in accordance with this invention, there are provided, as newcomyounds, bicyclic ester-lact-ones of the formula H; CH 0 -4 11 whereinR R and R are as above defined.

The alkyl A tetrahydro'phthalic anhydride reactants suitable for use inthis invention have alkyl groups on either one or both of the carbonatoms comprising the ethylenic unsaturation. There must be at least onealkyl group, as represented by R in the formula above, in order for theM-tetrahydrophthalic anhydride to be converted into the bicyclicester-lactone in substantial yield; A -tetrahydrophthalic anhydridesfree of such alkyl substitution cannot satisfactorily be converted intothe bicyclic ester-lactone. Thus, R in the formula above may be eitherhydrogen or alkyl but R must always be alkyl. The alkyl radicals, asrepresented by R and R are lower alkyl radicals and ordinarily are alkylradicals hav: ing not more than 6 carbon atoms. Examples of somesuitable alkyl radicals'include methyL'ethyl, isopropyl, butyl,tert-butyl, heXyl, and the like. The alkyl-A tetrahydrophthalicanhydrides are known to those skilled in the art and are readilyprepared by heating an alkylsubstituted butadiene, for example,2-methyl-1,3,-buta diene, with maleic anhydride, preferably in ahydrocarhon solvent.

The monohydric alcohol reactants for use in this invention comprise thehydrocarbyl alcohols such as the alkyl alcohols, e.g., methyl, ethyl,isopropyl, hexyl, decyl, dodecyl, tridecyl, and octadecyl alcohols;v thealkenyl alcohols, e.g., propenyl, methylallyl, pentenyl, andpentadecenyl alcohols; the cycloalkyl alcohols, e.g., cyclopentyl andcyclohexyl alcohols; the (cycloalkyl)alkyl alcohols, e.g.,cyclohexylethyl, cyclohexylbutyl, and cyclopentylpropyl alcohols; the(alkyl) cycloalkyl alcohols, e. g., l-methylcyclohexylmethyl, 1-1'-methylcycloheXyl) l-ethyl and 1-(2-ethylcyclohexyl)-3-propylalcohols; the aryl alcohols such as phenyl alcohol; the alkarylalcohols, e.g., methylphenyl, ethylphenyl, and dipropylphenyl alcohols;and the aralkyl alcohols, benzyl, butylbenzyl, phenylethyl, andphenylbutyl alcohols.

Although the alcohol reactants used in the process of this invention mayhave as many as 32 carbon atoms in the molecule, preferably the alcoholis one which has less than 18 carbon atoms per molecule. The alcohol maybe a straight-chain or a branched-chain one,

a and can be either a primary, secondary or tertiary alcohol. A verysuitable type of branch-chain alcohol is the 0x0 type alcohol producedby oxoration of an olefin or a lower olefin dimer, trimer, tetramer, orpentamer with carbon monoxide and hydrogen at a temperature betweenabout 250 C. and 450 C. under a pressure of about 150-400 atmospheres inthe presence of a cobalt or similar catalyst to form an aldehyde whichis then catalytically hydrogenated to form an alcohol as is well knownto those skilled in the art. For example, tridecyl alcohol is preparedfrom propylene tetramer or isobutylene trimer and carbon monoxide andhydrogen whereas hexadecyl alcohol is prepared from propylene pentamerand carbon monoxide and hydrogen.

The esterification and intramolecular cyclization reactions of thisinvention are usually carried out at a temperature below about 150 C.because the use of more elevated temperatures sometimes result in theformation of a substantial amount of the diester. The reactions can beconducted at temperatures as low as approximately room temperature e.g.,20 C.; however, it is usually desirable to use a temperature above roomtemperature, for example above 50 C., in order to have a relativelyshort reaction time. Ordinarily, these reactions are carried out atsubstantially atmospheric pressure although pressures above atmosphericmay be employed with the more volatile reactants.

Usually stoichiometric amounts of the alkyl-A -tetrahydrophthalicanhydride reactants and alcohol reactants are maintained in the reactionzone. However, it is sometimes desirable to use an excess of the alcoholreactant inorder to drive the anhydride-opening step to completion. Itis also possible to use an excess of the alkyl-A -tetrahydrophthalicanhydride although the use of an excess of this reactant is usually notdesirable since the unreacted material must be recovered in apurification step.

The partial esterification step of the process of this invention shouldbe conducted in a catalyst-free system since the use of a catalystpromotes the addition of 2 moles of the alcohol reactant to each mole ofthe alkyl-M-tetrahydroplrthalic anhydride reactant thereby effectingcomplete esterification of the latter and resulting in the formation ofa diester. The formation of the diester product is undesirable since thediester cannot be intramolecularly cyclized to form the desired bicyclicester-lactone.

The intramolecular cyclization step involved in the process of thisinvention must be carried out in the presence of an acid-type catalystin order to efiect formation of the bicyclic ester-lactone. Suitablecatalysts include the mineral acids such as hydrochloric, nitric,sulfuric, perchloric, and phosphoric acids; the sulfonic acids such asthe alkanesulfonic acids and the arylsul fonic acids; low molecularweight aliphatic carboxylic acids suchas formic and propionic acids; andsuli'onic type ion exchange resin materials, such as cross-linkedsulfonated polystyrene which is commercially available as Dowex-SO. Thealkanesulfonic acid catalysts are preferably the lower alkanesulfonicacids containing from 1 to 12 carbon atoms, for example, methanesulfonicacid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonicacid. If desired, a mixture of lower alkanesulfonic acids can be usedand such a mixture containing methane, ethane, and propanesulfonic acidsis commercially available. Ordinarily the alkanesulfonic acid willcomprise 92% to 95% sulfonic acid, from 1 to 2% sulfuric acid, and from3 to 6% water. The arylsulfonic acid catalysts which can be used in theprocess of this invention include the benzenesulfonic acids,toluenesulfonic acid, and chlorobenzenesulfonic acids, withp-toluenesulfonic acid and 4-chlorobenzenesulfonic acid being preferred.The amount of catalyst present in the reaction zone can be varied ,overwide limits depending upon the nature of the reactants and the catalystused. The amount of catalyst used is also determined to a considerableextent by the temperature selected for conducting the reaction. Thus, athigher temperatures the amount of catalyst required in the reaction zoneis smaller than when lower temperatures are used and the use ofexcessive amounts af catalyst at the more elevated temperatures willpromote the formation of undesired side products. Ordinarily the amountof catalyst used will be between about 0.1% up to 5% by weight of theamount of the alkyl-z -tetrahydrophthalic anhydride reactant.

The partial esterification and the intramolecular cyclization stepsinvolved in the process of this invention can be carried out eitherbatchwise or in a continuous manner. partial esterification step isconducted first and after the completion of this step, the catalyst isadded to the sysem in order ,to effect the intramolecular cyclization.Ordinarily, the partial esterification step will be completed in aperiod of time less than approximately one-half hour; however,substantially longer periods of time may be required in some cases withparticular reactants. The partial esterification step can be conductedover long periods of time if a suitable low temperature is used. Aftercompletion of the partial esterification step, the catalyst can be addeddirectly to the reaction zone without effecting any change in thereaction conditions. If desired, the reaction mixture obtained in theesterification step can be subjected to a separation step to effectremoval of any unconverted reactants. Although the catalyst promotes theformation of the diester product when the tetrahydrophthalic and alcoholreactants are brought together in the presence of the catalyst, there isno substantial formation of the diester product in the intramolecularcyclization step, depending upon the nature of the tetrahydrophtbalicanhydride, even though there is an excess of the alcohol reactantpresent in the reaction zone, because the intramolecular cyclizationstep occurs more readily than the partial esterification step underthese conditions.

If the process of this invention is carried out in continuous manner,the catalyst is preferably added to the system at a point aftersubstantial completion of the partial esterification step so as not tobe present in the system at a place where partial esterification of thetetrahydrophthalic anhydride and the alcohol takes place.

After completion of the intramolecular cyclization step, the reactionmixture is washed first with water to remove the acid catalyst and thenwith a dilute alkaline solution to remove any remaining catalyst andunreacted acid-ester and/or tetrahydrophthalic anhydride. Suitabledilute alkaline materials useful for this purpose include aqueous sodiumhydroxide, aqueous sodium carbonate, and aqueous calcium hydroxidesolution. After washing, the recovered material is purified in the usualmanner, such as by distillation, solvent extraction, or selective adsorption procedures.

The bicyclic ester-lactone products of this invention are stable liquidcompounds which range in color from colorless to a light yellow andwhich range in viscosity from very fluid to very viscous. The boilingpoints of these compounds are very high, usually above about 200 C.These bicyclic ester-lactones have good solvent prop erties and aresoluble in heptane, benzene, alcohols, ethers, ketones, and the like butare insoluble in Water.

The bicyclic ester-lactones of this invention are advantageously usedfor a variety of industrial purposes. The bicyclic ester-lactones ofthis invention are characterized by having low volatility and goodviscosity characteristics, therefore, finding use as functional fluidsin hydraulic fluid systems as Well as vacuum systems. Furthermore, thebicyclic ester-lactones of this invention find extensive use asplasticizers fo various synthetic resins, particularly the polyvinylhalide resins such as polyvinyl chloride, to form softened compositionsof inft the reactions are carried out batchwise, the.

creased resiliency and flexibility which is retained at low temperaturesas well as at high temperatures. The bicyclic ester-lactones of thisinvention are also compatible with other polymers such as polyvinylbutyral, cellulose acetate, cellulose acetate butyrate,'polystyrene andcertain polyacrylates.

The advantages, desirability and usefulness of the present invention areillustrated by the following examples.

Example 1 In this example, butyl 5-methyl-6-oxa-7-oxobicyclo[3.2.1.]octane-2-carboxylate, e.g., bicyclic ester-lactone, was preparedfrom 7,9-dioxo-4-methyl-8-oxabicyclo [4.3.0]-3-nonene, i.e., 4-methyl-A-tetrahydrophthalic anhydride, and n-butanol using 0.3 mole of eachreactant. The reactants were placed in a small flask and heated at atemperature in the range of 100-120 C. with stirring for a period of 1hour. During this heating step, the acidity of the reaction mixture waschecked periodically by titrating 0.5 ml. portions of the mixture with0.1 N-sodium hydroxide. The reaction mixture was then cooled and 1.8 gof sulfuric acid added to the reaction flask and heated for anadditional 1.5 hours at a temperature of 120 C. The acidity of thereaction mixture was periodically checked in this heating step as wasdone in the first heating step by titration with sodium hydroxide. Atthe end of 1.5 hours, the reaction mixture was dissolved in 50 ml. ofdiethyl ether and washed with 50 ml. of water followed by washing with50 ml. of 5% sodium hydroxide and two 50 ml. portions of water. Thecombined water phases were then washed with two 25 ml. portions ofdiethyl ether. The combined ether solutions were distilled under vacuumthrough a packed column to obtain the butyl S-methyl-6-oxa-7-oxobicyclo[3.2.l]octane-2-carboxylate boiling at 138-143" C./0.-2 mm. Hg andhaving a refractive index n 1.4743. Analysis of the product was found tobe 66.3% carbon and 8.1% hydrogen as compared with calculated values of65.0% carbon and 8.4% hydrogen.

Example 2 In this example, the butyl S-methyl-6-oxa-7-oxobicyclo[3.2.1]octane-2-carboxylate was prepared using the same reactions andconditions as were used in Example 1 except that the sulfuric acidcatalyst was replaced with 1 g. of 70% perchloric acid and thelactonization step was conducted at a temperature of 80 C. for a periodof time of 0.8 hour.

Example 3 In this example, tridecyl S-methyl-6-oxa-7-oxobicyclo-[3.2.1]octane-2-carboxylate was prepared from 7,9-diox-4-methyl-8-oxabicyclo[4.3.0]-3-nonene and tridecanol using 0.32 mole ofeach reactant. The reactants were placed in a small flask and heated ata temperature of 120 C. for 1 hour. Immediately thereafter, 100 ml. offormic acid was added to the hot reaction mixture and the heatingcontinued for a period of 6 hours while maintaining the temperature at100 C. Thereafter, the reaction mixture formed was diluted with 100 ml.of diethyl ether and washed with 100 ml. of water followed by washingwith 100 ml. of a solution of sodium hydroxide and another washing with100 ml. of water. The washed solution obtained was distilled, first in astill head to effect removal of the diethyl ether and the entrainedwater, and then at reduced pressure to obtain the tridecyl 5-methyl-6-oxa-7-oxobicyclo[3.2.1]octane 2 carboxylate boiling at 189-194C./0.25 and having a refractive index r2 1.4712. The yield of thebicyclic ester-lactone amounted to 61% The product had an analysis of72.2% carbon and 10.6% hydrogen as compared with calculated values of72.2% carbon and 10.4% hydrogen. The proposed structure was confirmed byan inspection of thev infrared spectrum of the product.

Example 4 In this example, the tridecyl5-methyl-6-oxa-7-oxobicyclo[3.2.1]octane-Z-carboxylate was preparedusing the same reactants and procedures as in Example 3 except that theheating in the first step was conducted for a period of time of 1.3hours instead of 1 hour and the formic acid catalyst was replaced with70% perchloric acid catalyst in an amount of 1 g. and the lactonizationwas conducted at a temperature in the range of -120 C. for a period oftime of 0.5 hour.

Reasonable variation and modification of the invention as described arepossible, the essence of which is that there have been provided: (1) aprocess for esterifying alkyl-A -tetrahydrophthalic anhydrides to formacid-esters thereof, (2) a process for reacting an alkyl-A-tetrahydrophthalic anhydride with a monohydric alcohol to form abicyclic ester-lactone, and (3) said bicyclic ester lactones as newcompounds.

We claim:

1. The method for producing a bicyclic ester-lactone, said methodcomprising (1) monoesterifying an alkyl- M-tetrahydrophthalic anhydrideof the formula C-CH C-Rz wherein R is the group C H where n is a wholenumber from 0 to 6, and R is an unsubstituted alkyl group containing upto 6 carbon atoms, with a monohydric unsubstituted alkanol containing upto 17 carbon atoms, wherein said anhydride and said unsubstitutedalkanol are present in about mole equivalent amounts, at a temperatureof from about 50 to about C. to form the acid-ester having the formulawherein R and R are as aboved defined, and R is an unsubstituted alkylradical containing up to 17 carbon atoms, and (2) then intramolecularlycyclizing said acidester at a temperature of from about room temperatureto about 150 C. in the presence of from about 0.1 to about 5 weightpercent, based on the said anhydride initially charged to the reactionmixture, of perchloric acid, as catalyst, to form a bicyclicester-lactone defined by the structural formula wherein R R and R are asabove defined, and recovering the said bicyclic ester-lactone asproduct.

2. The method for producing butyl 5-methyl-6-oxa-7-oxobicyclo[3.2.1]octane-2-carboxylate comprising (1) monoesterifying7,9-dioXo-4-methyl-8-oxabicyclo[4.3.0]- 3-nonene with n-butanol, whereinthe reaction compo nents are present in about mole equivalent amounts,at a temperature of from about 50 to about 150 C. to form an acid-esterproduct and (2) then intramolecularly cyclizing the acid-ester productat a temperature of from about room temperature to about 150 C. in thepresence of from about 0.1 to about 5 weight percent, based on the 7,9dioxo-4-methyl-8-oxabicyc1o [4.3.0]-3 nonene initially charged to thereaction mixture, of perchloric acid, as catalyst, to form the bicyclicester-lactone product butyl S-methyl 6 oxa-7-oxobicyclo[3.2.1]octane-2-carboxylate, and recovering the said bicyclic ester-lactone as product.

3. The method for producing tridecyl 5-methyl-6-oxa-7-oxobicyclo[3.2.1]octane-2-carboxylate comprising 1 monoesterifying7,9-dioxo-4-rnethyl-8-oxabicyc1o [4.3 .0] 3-nonene with tridecanol,wherein the reaction components are present in about mole equivalentamounts, at a temperature of from about 50 to about 150 C. to form theacid-ester product and (2) then intramolecularly cyclizing theacid-ester product at a temperature of from about room temperature toabout 150 C. in the presence of from about 9.1 to about 5 weightpercent, base-:1 on the 7,9-di0X0-4-methyl-8-oxabicyc1o[4.3.01-3-noneneinitially charged to the reaction mixture, of perchloric acid, ascatalyst, to form the bicyciic ester-lactone product tridecyl5-*nethyi-6-oxa-7-oxobicyclo[3.2.1]-octane- 2-carb0xylate, andrecovering the said bicyciic ester-lactone as product.

No references cited.

0 WALTER A. MODANCE, Primary Examiner.

1. THE METHOD FOR PRODUCING A BICYCLIC ESTER-LACTONE, SAID METHODCOMPRISING (1) MONOESTERIFYING AN ALKYL$4-TETRAHYDROPHTHALIC ANHYDRIDEOF THE FORMULA